Primate lentiviral Nef proteins deregulate T-cell development by multiple mechanisms

Area of Science:

• Immunology
• Virology
• Cell Biology

Background:

• The nef gene in primate lentiviruses like HIV and SIV is crucial for high viral loads and disease progression.
• Thymic infection by these viruses can decrease naive T-cell output, potentially causing immunodeficiency.
• Previous studies showed HIV-1 Nef can hinder human T-cell development, but mechanisms and conservation were unclear.

Purpose of the Study:

• To investigate if reduced thymic output is a conserved function of diverse primate lentiviral Nef proteins.
• To determine the specific mechanisms employed by different lentiviral Nef proteins in impairing T-cell development.

Main Methods:

• Expression of various lentiviral nef alleles (HIV-1, HIV-2, SIVcpz, SIVgor, SIVsmm, SIVmac239) in thymocyte progenitors.
• Analysis of T-cell development and thymic output in response to Nef expression.
• Mutagenesis studies to assess the role of PAK2 interaction and CD3 down-modulation.

Main Results:

• Most tested nef alleles impaired T-cell development and reduced thymic output.
• For HIV-1 Nef, binding to active PAK2 was a key factor in reducing thymic output.
• SIVmac239 Nef's effect on T-cell development was independent of PAK2 interaction, with CD3 down-modulation being sufficient.

Conclusions:

• Primate lentiviral Nef proteins impair T-cell precursor development through multiple mechanisms.
• HIV-1 Nef's detrimental effect is primarily mediated by active PAK2 interaction.
• CD3 down-regulation by HIV-2 and SIV Nef proteins is sufficient to reduce thymic output.
• The conserved function of Nef in reducing thymic output likely contributes to T-cell depletion in lentiviral infections.